1. Technical Field
The present disclosure relates to a light emitting diode (LED) lamp and, more particularly, to an LED lamp capable of emitting two lights with different color temperatures.
2. Description of Related Art
LEDs have been available since the early 1960's. Because of the relatively high light-emitting efficiency of LEDs, LED usage has been increased in popularity in a variety of applications, e.g., residential, traffic, commercial, industrial settings. With development of the semiconductor technology, nowadays LEDs could emit various colorful light, wherein white light is most preferable in general illumination for its color mostly similar to the sunshine. However, pure white light is not always popular in general illumination, sometimes the LEDs are designed to emit nonsolid white light for meeting particular color temperature requirements of some occasions. For example, orange-white light is more favorable in residential illumination for its warm color, while blue-white light could refresh people so it is widely used in office illumination.
A typical LED lamp often employs multiple white LEDs as the light source thereof. For ensuring a color consistency of the light output from the lamp, the LEDs used in the lamp are always selected to have the same spectrum, whereby the light produced by the lamp has a constant color temperature specified for a target occasion. However, sometimes the constant color temperature is not enough for some specific occasions, they may need more flexible illuminations with variable color temperatures. For example, a lamp switchable between a cold and warm color temperatures is more preferred in road illumination so that the lamp could be switched between the two color temperatures according to different weathers. Apparently, the typical LED lamp having the constant color temperature falls short of such a requirement.
What is needed, therefore, is an LED lamp which can overcome the above-mentioned disadvantages.